Well I'm glad to hear that sting/fiber/nettle is still 'in development' in general. I personally found the 'string' concept very hard at first as I didn't see any 'string making' skill and couldn't find anything called string as I wandered around eating spindly taproot for sustenance. Only consulting the wiki told me how the system worked. I'd rather have seen a "make string" option on taproot which would have created a string, even if I had to get a skill to be able to do it that would have given me some direction.
The real question should be "Are their meaningful classes of plant fibre?", is their some fibre you can make say a bow-string out of which is different from that which you can make linen out of or should all of these uses be interchangeable? Their are clearly some thing like animal sinew (HINT HINT loftar) that are appropriate for a string but not for linen so dose get a bit tricky. Best I can come up with now is that all Plant Fibre can be turned into "Plant Fiber String" and a number of other things can also be made into other things that end in the word string (so newbs know what they are used for), but not all these strings would necessarily be equivalent.